ackermann 0 0 => 1 
ackermann 0 1 => 2 
ackermann 0 2 => 3 
ackermann 0 3 => 4 
ackermann 0 4 => 5 
ackermann 1 0 => 2 
ackermann 1 1 => 3 
ackermann 1 2 => 4 
ackermann 1 3 => 5 
ackermann 1 4 => 6 
ackermann 2 0 => 3 
ackermann 2 1 => 5 
ackermann 2 2 => 7 
ackermann 2 3 => 9 
ackermann 2 4 => 11 
ackermann 3 0 => 5 
ackermann 3 1 => 13 
ackermann 3 2 => 29 
ackermann 3 3 => 61 
ackermann 3 4 => 125